/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.query.expression;

import org.apache.druid.error.InvalidInput;
import org.apache.druid.java.util.common.StringUtils;

import javax.annotation.Nullable;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

public class RegexpExprUtils
{
  /**
   * Compile the provided pattern, or provide a nice error message if it cannot be compiled.
   */
  public static Pattern compilePattern(@Nullable String pattern, String functionName)
  {
    try {
      return Pattern.compile(StringUtils.nullToEmptyNonDruidDataString(pattern));
    }
    catch (PatternSyntaxException e) {
      throw InvalidInput.exception(
          e,
          StringUtils.format(
              "An invalid pattern [%s] was provided for the [%s] function, error: [%s]",
              e.getPattern(),
              functionName,
              e.getMessage()
          )
      );
    }
  }
}
